Posted: 10/06/2013 at 08:02
This is a pretty good resource for all things garlic including tips on when to harvest. It is different depending on whether you have hard or softneck varieties.
They say that hardneck varieties are ready when the leaves start to change colour, and softneck is when they start to lay on the ground.
I bought my bulbs from them this year and the results (so far) have been far better than anything I have managed to produce in the past. Hopefully the same will be true when I get around to harvesting.